Back in the olden days, greenhouse gasses was produced only by nature via volcanic explosions.

But ever since engines appeared on the scene starting the Industrial Revolution of the late 17th, man has been adding greenhouse gasses to the environment at a staggering rate! (Engines are powered by fossil fuel a.k.a. oil which emits CO2, NO2, & etc.)

And eventhough some people mainly from the oil companies declares global warming as non-sense, there's tons of solid evidences that proves it for real!

For instance, the annual recording of global temperature since the mid-18th does show a pattern of incremental increase in global temperature.

Of course, it's no coincidence that the incremental increase coincided with the Industrial Revoltion - when man started burning fuel to run his industries (factories, machines, engines, & etc.) thereby putting more CO2 in the atmosphere which warms the Earth.